In end-to-end communication, for the sake of efficient communication, the smallest number of packets need to be transmitted, and thus packets with the largest packet size which can be supported in an end-to-end path need to be transmitted. The smallest one among maximum transmission units (MTUs) which can be supported in each link on a network path is referred to as a path MTU (PMTU). An IP packet transmission server transmits packets according to a PMTU to thereby transmit the smallest number of packets while avoiding an IP packet fragmentation.
In an Internet protocol version 4 (IPv4) unicast method, a PMTU can be detected using a traditional technique (RFC1063) established by the Internet engineering task force (IETF) in which an error message “Packet Too Big (PTB)” of an Internet control message protocol (ICMP) is used. However, a network operator and a network service provider currently do not support the ICMP due to a network security problem. Therefore, a method using the ICMP cannot actually be used.
A tool which detects a PMTU discovery failure, searches for a PMTU using a probe packet and ICMP feedback information and finds a PMTU discovery failure point was suggested by Matthew Luckie et al. in “Inferring and Debugging Path MTU Discovery Failures”, Internet Measurement Conference 2005 (IMC2005). However, this tool does not consider the multicast environment.
Recently, the IETF established a standard (RFC 4821) in which a PMTU is discovered by transmitting a probe packet to a network through a packetization layer such as a transmission control protocol (TCP). However, this standard mentioned the multicast environment but did not suggest a concrete technique.